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I have a UIView with several custom-drawed sublayers (a few CAGradientLayers with CAShapeLayer masks, etc.). I'm using the UIView animation method to animate it's bounds (increasing both its width and height). 

[UIView animateWithDuration:2 delay:0 options:UIViewAnimationOptionCurveEaseOut|UIViewAnimationOptionAutoreverse|UIViewAnimationOptionRepeat animations:^{
    CGRect bounds = myView.bounds;
    bounds.size.width += 20;
    bounds.size.height += 20;
    myView.bounds = bounds;
} completion:nil];

This works fine, except for the fact that the sublayers don't get redrawn as its animating. What the best way to do this? Do I need to setup some key-value observing detect bounds change and call setNeedsDisplay on all the sublayers?

zakdances
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2 Answers2

8

Set contentMode to UIViewContentModeRedraw on the view you are animating.

sixthcent
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4

Layers don't work like views. If you call setNeedsDisplay (which happends if you have set needsDisplayOnBoundsChange to YES) on the parent layer it will not affect the child layers. You need to call setNeedsDisplay them as well.

If your sublayers need to be resized as well when the parent layer is resized then implement layoutSublayers in the parent (or layoutSublayersOfLayer: in its delegate).

aLevelOfIndirection
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    You're right, but it still doesn't address the fact that there is a big difference between resizing a layer/sublayer and REDRAWING a layer/sublayer. My problem is that the layers (even with a valid delegate and needsDisplayOnBoundsChange = YES) don't call their drawLayer: method when their bounds ANIMATE. – zakdances Apr 14 '13 at 19:05
  • Are you implementing the drawing code in the drawLayer:inContext: within the delegate? – aLevelOfIndirection Apr 14 '13 at 19:11
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    Yes. It draws fine. It's only a problem when I animate the bounds. If I just change the bounds like self.layer.bounds = newBounds or self.bounds = newBounds it works fine on the immediately layer (although I have to manually change the sublayers like you said). – zakdances Apr 14 '13 at 19:13
  • You're actually right about needing to separately manage sublayers on iOS views. Add a line about how the bounds of layers don't continuously change duration animation (they only change on their presentationLayer) and I'll give you the green check. – zakdances Apr 14 '13 at 19:21
  • It's actually the case. The modelLayer gets the final animation value immediately while the presentationLayer gets the animated values. – aLevelOfIndirection Apr 14 '13 at 19:23